The use of the heat of adsorption of a liquid within a solar heating system is already known. U.S. Pat. No. 4,410,028 to Alefeld et al. discloses desorbing water from zeolite by the application of heat and obtaining the heat by adsorbing the water to obtain the heat of vaporization. U.S. Pat. No. 3,642,059 to Greiner discloses the adsorption of water on silica gel to obtain the heat of adsorption. U.S. Pat. No. 4,135,371 to Kesselring et al. discloses a heat storage system with adsorptive medium. A publication appearing in Solar Energy Vol. 23 entitled "Solar Energy Storage Using Chemical Potential Changes Associated With Drying of Zeolites" describes materials such as zeolites, alumina, charcoal and silica gel for adsorption of water and releasing heat. An article entitled "Super Cystals Generate Steam Heat" by David Scott appearing in the Mar. 19, 1980 issue of Popular Science discloses a commercially available system employing zeolites, pumps, heat exchangers and condensers capable of heating an entire house.
In each of the aforementioned Patents and publications, water is adsorbed on the adsorbing material until the material is saturated and the material is either displaced with dry adsorbent or a sophisticated heater and pump are employed to remove the water and to allow the adsorbing material to be activated for further adsorption.
In the absence of vapor transfer pumps and compressors, the materials listed in the aforementioned Solar Energy publication, for example, require temperatures in excess of the boiling point of water at atmospheric pressure to remove some of the water in order for the material to be activated for further adsorption. It would be highly desirable to use the heat of adsorption for solar energy purposes with materials that are capable of releasing water at temperatures slightly in excess of 70.degree. F. without the requirement of pumps, heat exchangers or compressors. This would allow the material to give off water under ambient sunlight conditions and to adsorb water after sundown and give off the stored solar heat as heat of adsorption.
The purpose of this invention is to provide a solar energy storage cell utilizing materials which are capable of releasing water under ordinary conditions of sunlight in a closed container and adsorbing water at sundown to release heat without requiring any of the water transfer apparatus suggested by the state of the art.